Complex computations can often be expressed a directed graph (called a “dataflow graph”), with components of the computation being associated with the nodes (or vertices) of the graph and data flows between the components corresponding to links (or arcs, edges) between the nodes of the graph. The components include data processing components that process the data and components that act as a source or sink of the data flows. The data processing components form a pipelined system that can process data in multiple stages concurrently. A system that implements such graph-based computations is described in U.S. Pat. No. 5,966,072, EXECUTING COMPUTATIONS EXPRESSED AS GRAPHS. In some cases, a graph-based computation is configured to receive a flow of input data and process the continuous flow of data to provide results from one or more of the components indefinitely until the computation is shut down. In some cases, a graph-based computation is configured to receive a batch of input data and process the batch of data to provide results for that batch, and then shut down or return to an idle state after the batch has been processed.